As with anything, quality materials are everything when it comes to successful outcomes. So, make sure you use a tubeless rim and really high quality rim tape with great valves. Never assume that you can get away with using a not-for-tubeless rim, a duct tape variant, or old, used up valves.
Want to save money? That's cool. We all do. Read THIS POST for great tips on how to get high-quality rim tape or sealant for your set up. Make sure you read the comments at the bottom for more great tips.
Side Note: If you are re-using a tire with a lot of old sealant in it, READ THIS POST for tips on how to remove old sealant.
For more on the preparation of you tire, rim tape installation, and valve core tips, read THIS POST. This is an over-all look at tubeless tire set-up, but the rim taping thing is in there.
Actually putting tape on a rim is an arduous task. My number one tip is to get prepped properly (cleaned rim, great tape, right tools) and use plenty of patience. Taping two rims is not a race. The ordinary rider should expect this to take up to and over a half an hour of your time. I know mechanics that will scoff at that, but they do things trying to be fast and efficient. People that are not mechanics don't have that constraint or need. Take your time taping and get it right.
Tools: I'll say it- a truing stand is your best friend here. You can tape a rim "free style", out of a bike, and you can tape a rim in a bike with it upside down on the floor. But a truing stand, properly affixed to a bench, makes taping a rim waaaaay easier. Obviously a truing stand is good for more than this, so seriously consider that as an upgrade to your shop.
Technique: The next big thing to add here is technique, and what I do is almost impossible without a truing stand, that's why I recommend a truing stand for your personal shop. I pull the tape gently with my right hand and hold the starting end down with my left thumb in the inner rim well. I pull maybe three inches, carefully align it, and pull it down toward the rim well. At the same time I start sliding my left thumb downward, but this is tricky as you have to not let the wheel rotate.
Once I lay the tape down on the rim then I use my left thumb or I'll use my right forefinger to press the tape down starting at the furthest point from the roll and working toward the roll. I only push it down in the center of the tape. I don't bother worrying about the edges until later.
I always put two laps of tape down on a rim. This is to help the tape withstand air pressure at the spoke holes. You could also use something like these Velocity Rim Plugs which would do the same thing. Another product that aims to alleviate the same problem is the WTB Solid Strip. By using these you might get away with one run of rim strip. However; I'd still use two runs of tape, because saving whatever weight using one run would give you, it is not worth it.
Rim tape should be wide enough that it covers up to where the bead of the tire will sit at a minimum and up to the rim's inner edge if at all possible. Never try overlapping tape to make it "wide enough". Get the right width rim tape instead.
Other than that, I always start taping at the point 180° from the valve stem. I've seen tape jobs that start near the valve stem, but in my opinion this invites a possible failure. Tape ends are prone to lifting and letting sealant seep between layers of tape or the tape and the rim well. If this occurs near a valve stem, a perfect place for pressure to escape, then you have a big problem. So, why not avoid that possibility and start your tape end at a point the furthest away from that big hole in the rim for the valve?
That's it. Did I miss anything you wanted to know? (Don't forget to check the links!) Hit me up in the comments.